Alkylbenzenes (phenyl-alkanes), especially where the alkyl group has 9 to 14 carbon atoms, have found many utilities, the most prominent of which is to make alkylbenzene sulfonates for use in laundry detergents and similar products. Alkylbenzenes are prepared by the alkylation of benzenes with mono-olefins of the desired molecular weight and configuration of the sought alkyl group. Typically these olefins are derived from a kerosene range fraction from a petroleum refining operation. This fraction is a paraffin-containing fraction and is subjected to dehydrogenation to generate the sought olefins.
In some instances it may be desired to locate an alkylbenzene facility at a location where a kerosene fraction is not readily available, or other commercial uses for a kerosene fraction render it less economically attractive as a feedstock for making alkylbenzenes. In these instances the ability to use alternative feedstocks is highly desirable.
Alternative feedstocks include other petroleum fractions, especially naphtha range fractions, and synthesized hydrocarbons such as Fischer-Tropsch materials. These raw materials have a lower molecular weight than the sought olefins for alkylation and accordingly must be subjected to a dimerization or a metathesis to generate olefins of suitable chain length (detergent range olefins). Numerous processes have been disclosed for preparing detergent olefins from these alternative feedstocks. See, for instance, WO 2004/072005, WO 2004/072006, and U.S. Patent Application Publications 2004/0030209, 2004/0176655, and 2004/0199035.
In order for alternative feedstocks to be viable as a source of detergent range olefins, not only must the synthesized olefin meet configurational requirements such as degree and type of branching, but also, the process must be technically feasible and economically competitive. By way of illustration, US 2004/0176655 discloses that the presence of oxygenated compounds and dienes is deleterious to the process and accordingly the feedstock is hydrogenated prior to a dehydrogenation to generate olefins for a dimerization. While this step effectively removes oxygenates and dienes, it also hydrogenates any olefins present in the feedstock and thus represents an operational inefficiency. US 2004/0030209 discloses, inter alia, preparing an olefin mixture of pentene and hexene for dimerization by the metathesis of a C4 olefin mixture. Butadiene and acetylenic compounds are removed by a selective hydrogenation.